The methods of electron diffraction and image processing are used to investigate the structure of cell membrane proteins at high resolution. A projection of the structure of bacteriorhodopsin has been obtained recently at approximately 4 A resolution, and work is in progress to extend these studies to a 3-D structure analysis. Other cell membranes being investigated include the pore-forming protein of E. coli outer membrane, gap junctions, and the crystalline patches in yeast plasma membrane.